Hello!

I am not new when it comes to Cryptocurrencies and stuffs but I don't have enough knowledge about Cryptography. May I ask if how a private key is generated with a seed phrase?

Someone told me I can use SHA256 to hash and get the output which is 64 characters(256 bits) and that is the private key. But I tried it on one of my unused wallets and used its mnemonic, and then used the SHA256 method but the hash generated is not the same with the original private key of the wallet. So how is a private key really generated from a mnemonic phrase?

P.S. I used a 12 word seed phrase.